About Lesson
Principles of Surveying
a. Location of a point by measurement from two points of reference
- The relative positions of new stations or points are located by measurements from at least two points of reference.
- The measurements can be either angular, linear or both. If we suppose P and Q can be two reference points on ground, then these are measured accurately and plotted on the sheet to some suitable scale. Now these points serve as reference points for plotting of other points. For plotting of other points, any of the following methods can be used.
b. Working from whole to part
- According to this principle, the whole area to be surveyed is first enclosed by control points (main stations) and control lines (main survey lines) which are established with higher precision.
- Once the major control points are established, then the minor control points are established from the major control points generally by running minor traverses. Only then the details are surveyed.
- Surveying proceeded in this way, localizes the errors and hence prevents accumulation of errors. If surveying is done in reverse trend that is from part to the whole there is accumulation of errors making the work uncontrollable.